Guide on using jest and fetch to properly validate the rendering of an APIgetMocking an API using jest and fetch for rendering verification

Despite conducting extensive research, I have been unable to find a concrete example that helps me understand this issue.

What I am aiming for is to mock the API and test if it is rendering correctly.

If someone could provide me with a code example using Jest specifically, it would greatly assist me in applying this knowledge to all other functions within my project. I am struggling to comprehend how to do this.

Thank you for your assistance.

REAL API from api folder

export const searchTrack = search => {
  return fetch(
    `${url}/search/tracks?q=${encodeURIComponent(
      search
    )}&limit=250&media=music`,
    {
      method: "GET",
      headers: {
        Authorization: Cookies.get("token")
      }
    }
  )
    .then(response => {
      return response.json();
    })
    .then(jsonFormat => {
      return jsonFormat.results;
    })
    .catch(() => {
      console.error("fetch for search dont work");
    });
};

addTracksPlaylist.vue method called

  methods: {
    search() {
      if (this.term !== "") {
        this.results = [];
        this.searching = true;
        apiPlaylist
          .searchTrack(this.term)
          .then(res => {
            if (res.status != 401) {
              this.searching = false;
              this.results = res;
              this.noResults = this.results.length === 0;
            }
          })
          .catch(() => {
            this.$router.push("/login");
          });
      }
    }
  }

I noticed that many people were creating a __mocks__ folder in the api directory, so I followed suit and created one with the appropriate API GET return values:


{
  wrapperType: "track",
  kind: "song",
  artistId: 461932,
  collectionId: 196480323,
  trackId: 196480329,
  artistName: "Europe",
  collectionName: "The Final Countdown",
  trackName: "The Final Countdown",
  collectionCensoredName: "The Final Countdown",
  trackCensoredName: "The Final Countdown",
  // More fields and values here...
}

Answer №1

When testing your function and needing to mock the response from a call to the searchTrack method, utilizing jest mocks can simplify this process.

To create a jest mock, simply use jest.fn().

You have the option to provide your own implementation using either of the following methods:

jest.fn(() => { //implementation goes here })

OR

jest.fn().mockImplementation(() => { //implementation goes here })

In order to mock an API response, ensure that your mock returns a Promise.

Consider something like the following approach:

jest.fn(() => Promise.resolve(mockDataValue))

Jest also offers a shortcut for this with the mockResolvedValue function.

jest.fn().mockResolvedValue(data)

This achieves the same goal. Additionally, there is the mockRejectedValue method available for testing error scenarios.

For further details, refer to the Jest Mock API Reference

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